Move theme-related helper methods out of controller (#37807)

spec/controllers/application_controller_spec.rb

@@ -85,20 +85,6 @@ RSpec.describe ApplicationController do
     end
   end
 
-  describe 'helper_method :current_theme' do
-    it 'returns "default" when theme wasn\'t changed in admin settings' do
-      allow(Setting).to receive(:default_settings).and_return({ 'theme' => 'default' })
-
-      expect(controller.view_context.current_theme).to eq 'default'
-    end
-
-    it 'returns instances\'s theme when user is not signed in' do
-      allow(Setting).to receive(:[]).with('theme').and_return 'contrast'
-
-      expect(controller.view_context.current_theme).to eq 'contrast'
-    end
-  end
-
   context 'with ActionController::RoutingError' do
     subject do
       routes.draw { get 'routing_error' => 'anonymous#routing_error' }

spec/helpers/theme_helper_spec.rb

@@ -100,6 +100,60 @@ RSpec.describe ThemeHelper do
     end
   end
 
+  describe '#current_theme' do
+    subject { helper.current_theme }
+
+    context 'when user is not signed in' do
+      context 'when theme was not changed in settings' do
+        it { is_expected.to eq('default') }
+      end
+
+      context 'when theme is changed in settings' do
+        before { Setting.theme = 'contrast' }
+
+        it { is_expected.to eq('contrast') }
+      end
+    end
+
+    context 'when user is signed in' do
+      before { allow(helper).to receive(:current_user).and_return(current_user) }
+
+      let(:current_user) { Fabricate :user }
+
+      context 'when user did not set theme' do
+        it { is_expected.to eq('default') }
+      end
+
+      context 'when user set theme' do
+        before { current_user.settings.update(theme: 'alternate', noindex: false) }
+
+        context 'when theme is valid' do
+          before { allow(Themes.instance).to receive(:names).and_return %w(default alternate good evil) }
+
+          it { is_expected.to eq('alternate') }
+        end
+
+        context 'when theme is not valid' do
+          it { is_expected.to eq('default') }
+        end
+      end
+    end
+  end
+
+  describe '#page_color_scheme' do
+    subject { helper.page_color_scheme }
+
+    context 'when force_color_scheme is present' do
+      before { helper.content_for(:force_color_scheme) { 'value' } }
+
+      it { is_expected.to eq('value') }
+    end
+
+    context 'when force_color_scheme is absent' do
+      it { is_expected.to eq('auto') }
+    end
+  end
+
   private
 
   def html_links